This section provides background information related to the present disclosure which is not necessarily prior art.
Applications for an elastomeric bushing assembly include, but are not limited to, torsion bars, linear torque rods, V-shaped torque rods, leaf springs, independent suspension control arms and other suspension control devices. These and other applications are used on a wide variety of vehicles such as trucks, buses, off-highway vehicles, rail cars and other transportation applications.
Elastomeric bushing assemblies include an outer metal, an inner metal and an elastomeric bushing disposed between the outer metal and the inner metal. The outer metal can be a tubular member which is a part of the component that incorporates the elastomeric bushing assemblies or the outer metal can be a separate tubular member that is designed to be assembled to the component that incorporates the elastomeric bushing assembly by being press fit or otherwise attached to the component.
The inner metal is a solid tubular member which is adapted to be secured to the vehicle and/or suspension member of the application which includes the component that incorporates the elastomeric bushing assembly. One example of an inner metal is a bar pin that has a cylindrical or spherical center section and a flat section disposed at both ends of the center section. The flat sections extend out from the center section of the outer metal and each flat section defines a hole which is used to secure the elastomeric bushing assembly to the vehicle and/or the suspension member of the application.
The solid bar pin can be machined from bar stock, it can be cast, it can be forged or it can be manufactured by other methods in the art. If necessary, the formed solid bar pin can be machined at the flat sections and/or the center section to complete the manufacture of the bar pin.
The transportation industry continually strives for cost and weight savings to improve vehicle performances. The solid bar pin is both heavy and expensive due to both the initial forming as a solid component and the subsequent machining operations.
Various attempts have been made at producing bar pins that have a hollow center section. One design starts with a steel tube. Both ends of the steel tube are crushed to form the flat sections. While these bar pins have had limited success, their strength is limited. In order to form the flat sections, the steel tube must be crushed flat and thus the thickness of the flat section is limited to two wall thicknesses of the steel tube. This limited thickness may not be able to withstand the loading requirements for the elastomeric bushing assembly.